Try moving it to a sunnier area. Monarda wants as much sun as possible and this might strengthen the stems.

Larry

"Try moving it to a sunnier area" - hmmph, give me more land, or move the neighbor's townhouse further away! Maybe I should plant the white-flowered Monarda clinopodia, which I believe is the only Monarda species whose natural habitat is "open woodland" / light shade. If I try another cultivar, I will make sure that it is described as maximum height 3 feet or under, as well as mildew-resistant.

Actually, I found that some normally tall perennials "flop" so badly in shady areas that the stems just trail along the ground. I have removed some plants for this reason. My garden has gotten noticeably shadier in the last four years as the trees have grown (almost completely surrounded by townhouses + trees).

Pour the water from rinsing milk cartons/jugs over the mildewy plants. Next year start sooner. It really will help!

Or mix 1/2 cup any milk product per gallon of water and spray.

"Pour the water from rinsing milk cartons/jugs over the mildewy plants." But won't that attract cats to the garden? (Just kidding)

'Jacob Cline' is a known mildew resistant cultivar, and I had excellent results with it a few years ago. (I eventually removed it to make room for other plants.)

Thanks for your suggestions. I plan to keep the M. fistulosa, remove the Bluestocking, and plant a red, hopefully mildew resistant variety such as Jacob Kline, Gardenview Scarlet, or Raspberry Wine. I would like to attract hummingbirds, which I know are in the area but don't see often, and red Monardas are supposed to be among the best hummingbird flowers. I will also prune them to maintain at a shorter and steadier height.

I have Bluestocking, and it doesn't powdery-mildew until September. And everything else powdery-mildews in September anyway in my garden. It's growing in full sun, though.